The present invention is related to industrial process control and measurement devices. More particularly, the present invention is related to an integrated device that controls fluid flow therethrough.
Field devices, such as process variable transmitters, are used by a number of industries to remotely sense or control a process variable. Such variables are generally associated with fluids such as slurries, liquids, vapors, gasses, chemicals, pulp, petroleum, pharmaceuticals, food, and other fluid processing plants. Process variables may include pressure, temperature, flow, turbidity, density, concentration, chemical compensation, and other properties. Other examples of field devices include valves, actuators, heaters, and controllers.
In the past, an industrial process fluid flow control system generally required multiple components. For example, a first field device, such as a process variable fluid flow transmitter would have a fluid obstruction device, such as an orifice plate, disposed in the fluid flow. The flow transmitter would then measure differential pressure across the fluid flow device and calculate the mass flow of the fluid passing therethrough. The flow transmitter would then convey the fluid flow information to a process controller, which may be a computer located in a control room, or even another field device mounted in the field. The controller would then apply a control algorithm to both the flow measurement information received from the process fluid flow transmitter and a known flow set point provided to, or otherwise known by, the controller. The controller then generates a fluid flow output that is conveyed to yet another field device, generally a valve, to modify the fluid flow through the system based upon the applied control algorithm. Such a closed-loop fluid flow control system is known in the art.
Recently, iris-diaphragm control valves have been used in conjunction with flow measurement to provide systems that can regulate fluid flow. Iris-diaphragm control valves are similar in concept to the optical shutter of a camera. The iris is generally comprised of three or more fingers that extend into the flow area and obstruct fluid flow through the flow area. One such iris-diaphragm control valve is sold by the Emile Eggar and Ciesa Pump and Machine Manufacturers in Switzerland. While work has been done to provide closed-loop fluid flow control systems using iris-diaphragm control valves, there is significant need for improvements. For example, each different device in the flow control system introduces additional costs as well as additional process fluid seals that may fail. Further, each process device used in a flow control system will also require additional technician time for installation and/or maintenance.